Along with his friend and team-mate, Eric Brandon, Brown was a star of the 500 cc championships with his F3 Cooper, his personal highlight in this category being a win in the 1951 Luxembourg GP.

For 1952 he teamed up with Brandon to race the new F2 Cooper-Bristols under the Ecurie Richmond banner, but they were effectively works machines. Things started well when Brown scored two points on the car's Continental debut at Bremgarten and followed this with two sixths, at the Monza Autodrome GP and the Belgian GP at Spa, but it was steadily overtaken by more sophisticated machinery, encouraging Alan to look elsewhere for racing success. He gave the prototype Vanwall its debut at the 1954 International Trophy, and raced a Connaught at the same event a year later, but he concentrated on sports cars - Coopers and Connaughts from 1953 to 1955 and then a Jaguar D-Type in 1956, his last season of racing.

He then went on to enter Formula 2 Coopers, giving rides to many aspiring racers, including Innes Ireland, Ken Tyrrell, Peter Ashdown and Mike Taylor.